1. Field of the Invention
The present invention relates to an apparatus for charging products to be frozen onto a freezer plate extending in a horizontal plane and arranged in a freezer housing defining a charging opening in this plane.
2. Description of the Prior Art
Freezers which comprise a stack of horizontally extending hollow freezer plates, through which a refrigerant fluid circulates and which are vertically movably mounted in an insulated freezer housing are well known. The freezer housing has a front wall and a rear wall respectively defining a charging opening for receiving the products to be frozen from a charging conveyor and a discharge opening through which the frozen products are discharged onto a discharge conveyor. Means is provided for vertically displacing the stack of freezer plates in increments to move the freezer plates successively to the level of the openings and for transferring the products to be frozen from the charging conveyor through the charging opening onto the freezer plate moved to this level and for simultaneously transferring the frozen products from this freezer plate through the discharge opening onto the discharge conveyor. The charging conveyor is normally a horizontally extending endless conveyor belt and a pusher bar transfers the products to be frozen from the conveyor belt to the freezer plate. These products are arrayed on the conveyor belt side-by-side in a row and the length of the row is equal to the useful width of the freezer plate so that all the products are charged at the same time as the pusher bar pushes the row of products through the charging opening. As the row of products is pushed in through the charging opening in the front wall of the freezer housing, a row of frozen products at the other end of the freezer plate is simultaneously pushed out through the discharge opening in the rear wall, rows of products being arranged side-by-side on the freezer plate in a continuous freezing operation
The translatory movement of the pusher bar required for charging and discharging row after row of products is relatively short. However, the pusher bar is generally also used for completely emptying the freezer before stopping the freezing operation, for example to defrost the freezer. Therefore, the translatory movement stroke of the pusher bar must exceed the length of the freezer plates (3 to 4 meters). For this reason, it is not possible to use conventional jacks for driving the pusher bar and, generally, special drive chains are utilized, which curvilinearly extend in only one direction from their rectilinear course so that they may exert traction as well as pushing forces under certain operating conditions. These chains, like racks, are moved by sprocket gears which engage the rectilinear and horizontal section of the chains, and the ends of the chains are attached to the pusher bar. Behind the sprocket gears, the chains are guided in shafts which are upwardly curved to reduce obstruction. The sprocket gears engage the chains only with one or two gear teeth and, therefore, the force they can exert upon the pusher bar is limited. However, sometimes it is necessary to exert considerable pushing force upon the bar to detach the frozen products from the freezer plate before charging the plate again, and this may be impossible with an arrangement such as disclosed, for example, in U.S. Pat. No. 3,557,975.